Reconfigurable terahertz Vivaldi antenna based on a hybrid graphene‐metal structure

This paper presents a reconfigurable terahertz Vivaldi antenna based on a hybrid graphene‐metal structure. The proposed antenna uses a novel tapered slot edge with hybrid graphene‐metal structure to improve the electromagnetic characteristics of classical metallic Vivaldi antennas. The results show that the proposed hybrid graphene‐metal Vivaldi antenna can be dynamically reconfigured via electric field bias, and has a low reflection coefficient. Moreover, this study demonstrates that the proposed antenna has excellent gain and radiation efficiency than that of the graphene Vivaldi antenna, and brings more possibilities to the realization and application of graphene antennas in the terahertz band, which is expected to use in terahertz wireless communication in the future.     

Generalized Pareto ranking bisection for computationally feasible multiobjective antenna optimization

Multiobjective optimization (MO) allows for obtaining comprehensive information about possible design trade‐offs of a given antenna structure. Yet, executing MO using the most popular class of techniques, population‐based metaheuristics, may be computationally prohibitive when full‐wave EM analysis is utilized for antenna evaluation. In this work, a low‐cost and fully deterministic MO methodology is introduced. The proposed generalized Pareto ranking bisection algorithm permits identifying a set of Pareto optimal sets of parameters representing the best trade‐offs between considered objectives. The subsequent designs are found by iterative partitioning of the intervals connecting previously obtained designs and executing Pareto‐ranking‐based poll search. The initial approximation of the Pareto front found using the bisection procedure is subsequently refined to the level of the high‐fidelity EM model of the antenna at hand using local optimization. The proposed framework overcomes a serious limitation of the original, recently reported, bisection algorithm, which was only capable of considering two objectives. The generalized version proposed here allows for handling any number of design goals. An improved poll search procedure has also been developed and incorporated. Our algorithm has been demonstrated using two examples of UWB monopole antennas with four figures of interest taken into account: structure size, reflection response, total efficiency, and gain variability.     

Integrated structure-electromagnetic optimization of large reflector antenna systems

A novel multiparameter optimization method is developed for use with terrestrial and space reflector antenna electromechanical systems and other metallic and composite engineering structures. To satisfy extremely high design requirements, the proposed approach incorporates the objectives from various structural and electromagnetic (EM) performances of the system at many working/loading cases simultaneously. A finite element method is used for structural analysis. Optical ray tracing, spline function aperture field interpolation, geometric optics aperture integration, and FFT techniques are employed to analyse the EM performances of distorted reflector antennas. A systematic method is used for parameter profile analysis of the system. The optimization involves member size, structural geometric and material design variables. Various terrestrial and orbital working environments and loading cases which affect antenna performances can be included in the optimization model. The optimization of an 8 m antenna system, as an example, is discussed and the results are given.     

Improved trust‐region gradient‐search algorithm for accelerated optimization of wideband antenna input characteristics

Full‐wave electromagnetic (EM) simulation models are ubiquitous in carrying out design closure of antenna structures. Yet, EM‐based design is expensive due to a large number of analyses necessary to yield an optimized design. Computational savings can be achieved using, for example, adjoint sensitivities, surrogate‐assisted procedures, design space dimensionality reduction, or similar sophisticated means. In this article, a simple modification of a rudimentary trust‐region‐embedded gradient search with numerical derivatives is proposed for reduced‐cost optimization of input characteristics of wideband antennas. The approach exploits information and history of relative changes of the design (as compared with the trust region size) during algorithm iterations to control the updates of components of the antenna response Jacobian, specifically, to execute them only if necessary. It is demonstrated that the proposed framework may lead to over 50% savings over the reference algorithm with only minor degradation of the design quality, specifically, up to 0.3 dB (or <3%). Numerical results are supported by experimental validation of the optimized antenna designs. The presented algorithm can be utilized as a stand‐alone optimization routine or as a building block of surrogate‐assisted procedures.     

Wire antennas optimized using genetic algorithm

In this work, wire antennas are designed to jam GSM frequencies using genetic algorithms. These antennas are designed to block communication at 3-band GSM frequencies. They are planned to be mounted on a vehicle and therefore are modeled on a ground plane. Jammer antennas designed in this work are composed of wires, placed on two square dielectric frames, perpendicular to each other. Genetic optimization routines are developed on MATLAB environment for the designs carried out in this work. Electromagnetic simulation program called SuperNEC, which analyses antennas by the method of moments, is used to determine the antenna performances and is called by the developed GA routines. The purpose of the antenna optimization is to obtain low VSWR values and omni-directional radiation pattern near ground at θ = [70° 80° 90°] planes at all GSM frequencies, since the targets will be near ground for this application. Original and interesting antenna designs are obtained as the result of genetic optimization, and are presented in the paper.     

Cost effective Android-Antenna Tool (AAT) for the parameter calculation of antenna in android platform

Mobile technology evolution and mobile based education are highly needed for academic system. Especially designing a physical antenna is a tough task so that Simulation solution has been used in the laboratory. Even though it is costlier and it could be used only in LAN based computers for an academic purpose but not used in outside. To be clear, the designing of an antenna with institution studies are needed. To overcome and achieve the objective of the paper which proposes to develop a mobile based designing antennas such as Dipole, Loop antennas. The performances of antenna have been carried out in mobile platform. This is an attempt to predict parameters of specified antenna in the android platform. Through this application the students could able to predetermine the characteristic of specified antenna easily. This application will be highly useful and recommended to the students. The proposed work has been designed by Eclipse software and Android studio software. Finally the performance of the antenna parameters has been carried with the help of Android-Antenna Tool (AAT).     

基于石墨烯材料的太赫兹波段频率可重构八木天线

传统天线中使用电子开关或PIN二极管开关等方式实现天线可重构功能,但是在太赫兹波段上会面临切换速度慢,偏置电路复杂等问题。石墨烯具有优异的电磁性能,可运用于太赫兹可重构天线中。根据石墨烯表面电导率模型,研究其电导率随频率、化学势的变化关系,证明了石墨烯在可重构天线设计中的可行性。设计了一款太赫兹波段石墨烯频率可重构八木天线,通过改变石墨烯贴片偏置电压改变石墨烯化学势,从而改变天线的工作模式。在HFSS软件中进行仿真优化,天线具有300GHz和500GHz两种频率的工作模式,最大增益分别达到9.29dB和10.28dB,表现出良好的辐射特性。     

Expedited simulation‐driven design optimization of UWB antennas by means of response features

In this work, a method for fast design optimization of broadband antennas is considered. The approach is based on a feature‐based optimization (FBO) concept where reflection characteristics of the structure at hand are formulated in terms of suitably defined feature points. Redefinition of the design problem allows for reducing the design optimization cost, because the dependence of feature point coordinates on antenna dimensions is less nonlinear than for the original frequency characteristics (here, S‐parameters). This results in faster convergence of the optimization algorithm. The cost of the design process is further reduced using variable‐fidelity electromagnetic (EM) simulation models. In case of UWB antennas, the feature points are defined, among others, as the levels of the reflection characteristic at its local in‐band maxima, as well as location of the frequency point which corresponds to acceptable reflection around the lower corner frequency within the UWB band. Also, the number of characteristic points depends on antenna topology and its dimensions. Performance of FBO‐based design optimization is demonstrated using two examples of planar UWB antennas. Moreover, the computational cost of the approach is compared with conventional optimization driven by a pattern search algorithm. Experimental validation of the numerical results is also provided.     

Fast simulation‐driven antenna design using response‐feature surrogates

In this article, a computationally efficient procedure for electromagnetic (EM)‐simulation‐driven design of antennas is presented. Our methodology is based on local approximation models of the antenna response, established using a set of suitably selected characteristic features rather than the entire response (such as reflection versus frequency). The approximation model is utilized to verify the level of satisfying/violating given performance requirements, and to guide the optimization process towards a better design. By exploiting the fact that the dependence of the response features on the designable parameters of the antenna of interest is simple (close to linear or quadratic), the feature‐based optimization converges faster than conventional optimization of frequency‐based EM‐simulated responses. In order to further speed up the design, coarse‐discretization simulations are utilized to estimate the feature gradients with respect to adjustable parameters of the problem at hand. The optimization algorithm is embedded in the trust‐region framework for safeguarding convergence. The proposed technique is demonstrated using two antenna examples. In both the cases, the optimum design is obtained at the computational cost corresponding to a few high‐fidelity EM antenna simulations. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:394–402, 2015.     

基于能量收集的环境反向散射通信联合优化算法设计

针对环境反向散射通信系统,设计两跳无线信息和能量传输方案并基于能效最大化准则给出联合优化算法。源端配置多天线并采用最大比发送(Max Ratio Transmission,MRT)预编码方法,中继节点使用功率分流法以完成信息发送与能量收集。基于系统传输模型,对源端天线数和发送功率采用联合优化算法以得到系统最大能效。借助高信噪比近似法进行非凸向凸的转化以解决优化目标中非凸问题。此外,利用Lambert W函数得到源端天线数和发送功率联合优化的最优解。仿真结果验证了所提方案的有效性和正确性。     

Design and optimization of a modified Sierpinski fractal antenna for broadband applications

Immense understanding of antenna designers illustrate that a general microstrip antenna demonstrate low efficiency. Various techniques have been adopted to improve the performance characteristics of microstrip antenna. This paper deals with the optimization of Sierpinski fractal antenna structure by utilizing the particle swarm optimization (PSO) and curve fitting method. The required data for optimization and fitting the curve has been obtained by varying different design parameters of the proposed antenna. Electromagnetic solver Ansoft HFSS 13.0 is used for generating the parametric data. The MATLAB curve fitting tool is referred for developing the equations which exhibits the relations between the parameters of proposed antenna design. Particle swarm optimization technique is then applied to find the optimum values of the design parameters for the bandwidth enhancement of proposed antenna. Curve fitting based optimized design represents the remarkable improvement in the bandwidth of conventional microstrip line fed Sierpinski fractal antenna for broadband applications.     

一种宽频带复合天线设计

针对多系统载体天线数量多的问题,提出了一种基于印刷振子结构的宽频带共口径复合天线设计方法;通过两种不同形式的印刷偶极子进行共口径设计：采用平面印刷偶极子结构完成宽带高增益线极化天线,通过宽带定向耦合器实现了天线和差方向图辐射;采用十字印刷偶极子实现低增益天线的圆极化辐射;两种天线单元印刷在同一微波介质上,通过优化天线单元布局,相对位置关系和增加金属隔离环等措施,降低天线之间的相互影响,实现共口径复合天线性能满足工程应用要求;加工了天线样机,测试结果表明线极化天线在工作频带1.2～1.8 GHz范围内和差通道电压驻波比小于1.8,和通道增益大于13.5 dBi,方位差波束零值深度小于-25 dB,圆极化天线在工作频带1.2～1.8 GHz范围内电压驻波比小于1.6,增益大于6.5 dBi,轴比小于2.5 dB,与计算结果基本一致;复合天线可以满足多种无线通信系统的需求,减少了天线数量,有效节省载体平台空间,同时具有结构简单紧凑、剖面低、易于工程实现等特点,具有广阔的应用前景。     

Simulation‐based optimization for rigorous assessment of ground plane modifications in compact UWB antenna design

Introducing ground plane modifications is a popular approach in the design of compact UWB antennas. Yet, specific topological alterations are normally reported on case to case basis without thorough investigations concerning their general suitability for antenna miniaturization. In particular, detailed performance comparison of different ground plane modifications is lacking in the literature. In this article, the effect of selected ground plane modifications on achievable miniaturization rate is considered based on a set of four UWB antennas. EM‐driven optimization is carried out to minimize the antenna footprints while maintaining acceptable matching within the UWB frequency range. In each case, all geometry parameters of the respective structures are utilized in the design process. For the sake of fair comparison, all antennas are implemented on the same dielectric substrate. Our results indicate a clear performance pattern, here, an advantage of the elliptical ground plane slit below the feed line over the rectangular one (average size reduction ratio of 26% versus 19% across the benchmark set). Our conjectures are confirmed by physical measurements of the fabricated antenna prototypes.     

数字化相控阵天线远场测试系统设计

数字化相控阵天线广泛运用于各种相控阵雷达当中,针对数字化相控阵天线测试过程数据量大、耗时长、自动化程度不足的现状,提出了一种数字化相控阵天线远场测试系统设计方案,并进行了测试系统开发验证.系统采用六轴工业机器人、三轴扫描架、冷水机、矢量网络分析仪、功率放大器、电源等设备模块集成并布置于暗室中,测试软件系统采用模块化设计方法,利用多线程技术实现测试设备模块并行调用,实现多频点、多波位、多通道同步测试以及测试过程时序的优化.系统具备良好的维护性和拓展性,集成多样化的测试参数配置和显示界面接口,实际应用表明数字化相控阵天线测试系统能满足相控阵天线方向图测试的各项指标要求,和传统方案相比操作简单、自动化程度高,能较大程度地提高测试效率.     

CSRR based folded monopole tri‐band antenna array and its system level evaluation

In this article, a folded monopole antenna loaded with complementary split ring resonators (CSRRs) is proposed for tri‐band applications. The two bands of the antenna are generated by the folding of the monopole (first band is caused due to fundamental mode and another due to higher order mode) and CSRRs have been responsible for the third band. By using four such antennas in form of an array, the gain and bandwidth have been improved. The prototype of the antenna array is developed on FR4 substrate and simulated results are experimentally validated. A simplified equivalent circuit model of the antenna has been developed and analyzed to quantify the power loss due to input impedance mismatch at each resonance frequency. By using the EM model of the proposed antenna in the Keysight ADS verification test bench its suitability to operate in the system environment has been confirmed.     

Phase‐spacing optimization of linear microstrip antenna arrays using simulation‐based surrogate superposition models

A technique for simulation‐driven optimization of the phase excitation tapers and spacings for linear arrays of microstrip patch antennas is presented. Our technique exploits two models of the array under optimization: an analytical model which is based on the array factor, as well as an electromagnetic (EM) simulation‐based surrogate model of the entire array. The former is used to provide initial designs which meet the design requirements imposed on the radiation response. The latter is used for tuning of the array radiation response while controlling the array reflection response as well as for validation of the final design. Furthermore, the simulation‐based surrogate model allows for subsequent evaluation of the array responses in the beam scanning operation at negligible computational costs. The simulation‐based surrogate model is constructed with a superposition of simulated radiation and reflection responses of the array under design with only one radiator active at a time. Low computational cost of the surrogate model is ensured by the EM‐simulation data computed with coarse meshes. Reliability of the model is achieved by means of suitable correction carried out with respect to the high‐fidelity array model. The correction is performed iteratively in the optimization process. Performance, numerical efficiency, and accuracy of the technique is demonstrated with radiation pattern synthesis of linear arrays comprising 32 microstrip patch antennas by phase‐spacing optimization. Properties of the optimal designs in the beam scanning operation are then studied using the superposition models and compared to suitably selected reference designs. The proposed technique is versatile as it also can be applied for simulation‐based optimization of antenna arrays comprising other types of individually fed elements. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:536–547, 2015.     

环型桁架卫星天线的非线性动力学分析

我国航天工业迫切需要掌握可入轨后展开的大型网架式空间结构技术,而环形桁架可展天线具有应用空间大、结构形式简明的特点,是目前大型卫星天线较为理想的结构形式~([1-3]).本文基于Zhang et al建立的环形天线模型为研究对象并在此基础上建立了天线振动时的非线性常微分运动方程,运用matlab数值模拟方法研究了热激励对系统非线性动力学行为的影响.     

Spectral efficiency enhancement using an antenna‐based orthogonal frequency division multiaccess technique

An approach to enhance antenna spectral efficiency is proposed based on combining spacetime electromagnetic (EM) models of Tx/Rx antennas with orthogonal frequency division multiaccess (OFDM), leading to the EM‐OFDM, a technology capable of removing intersymbol interference (ISI) in high‐data rate communication links caused by the EM‐induced distortion antenna effects. The proposed approach differs from traditional OFDM in wireless communication in several aspects. First, the technique suggests a new decoupling approach by treating each given antenna transreceive device pair as a “stand‐alone channel” with its own distortion mechanisms considered separately from the propagation channel. Moreover, the deterministic distortion caused by the nonflat pure antenna EM filtration effects is exploited to carefully design a specialized OFDM transmission techniques based on the antenna parameters, not the multipath fading channels often invoked in conventional uses of OFDM methods. (The EM‐OFDM, however, can be combined with a traditional OFDM later if fading channels are present.) In this manner, a more efficient implementation of the wireless link equalization strategy may be enacted since the EM antenna origin of ISI is very different from the traditional propagation channel one. As a proof of concept, the proposed EM‐OFDM method is implemented for a single‐input‐single‐output link comprised of half‐wavelength linear wire antennas. A careful use of finite difference time‐domain to provide EM data allowed the construction of 64 decoupled “pure antenna OFDM subchannels.” Simulation results suggests that the antenna‐based OFDM system is capable of completely neutralizing all ISI effects caused by the limited antenna matching bandwidth of the transreceive wires, therefore, supporting considerably higher data rates with low symbol error rate (SER). A concrete evaluation of the SER using quadrature phase‐shift keying (QPSK) digital carrier modulation resulted in an increase of the effective antenna digital communication spectral efficiency by ratios up to 300%. Moreover, the EM‐OFDM error rate was found to be close to the ideal QPSK level or the maximum possible theoretical limit. Thus, combining detailed EM knowledge with standard signal processing methods can lead to considerable improvement in system design without modifying the antenna physical layout. The proposed approach is expected to play a role in the forthcoming 5G/6G and millimetre wave technology systems currently under development where there is a trend toward integration of EM and digital signal processing at the physical layer level.     

基于HFSS的漏波长槽波导天线的口径场诊断

介绍HFSS在漏波长槽波导天线口径场诊断中的应用,通过合理的子网格设置仿真得到辐射长槽上精确的口径场。采用提取的口径场分布反演得到天线远场方向图,将其与仿真得到的方向图相比,非常吻合,证明这种诊断方法正确有效。根据口径场诊断结果,对天线结构进行调整优化,达到明显的优化效果,天线副瓣明显降低,负载吸收率与理论设计非常吻合。     

Performance comparison of bio-inspired optimization algorithms for Sierpinski gasket fractal antenna design

The Sierpinski gasket fractal antenna is most popular structure in the domain of fractal antennas. This fractal antenna has multi-band performance, and hence, the design of this antenna for the desired frequencies is a challenging problem. The artificial intelligence tools like artificial neural networks, fuzzy logic systems, bio-inspired optimization techniques are appropriate to provide accurate design solution in such cases. In this paper, three most popular bio-inspired optimization algorithms: genetic algorithms, particle swarm optimization (PSO), and bacterial foraging optimization, have been proposed to solve the design issues of Sierpinski gasket pre-fractal antenna. Their performances are analyzed and are compared with the experimental results. A simplified expression for calculation of resonant frequency of Sierpinski gasket pre-fractal antenna is proposed and is used as the objective function. Finally, the effectiveness is compared on the basis of three different measures: mean absolute percentage error, the average time taken by the models to evaluate the results, and the coefficient of correlation. The results indicate that the PSO algorithm is most suitable for this type of antenna.